Phase I research adapted primary culture methods to obtain a reliable source of normal ectocervico-vaginal (ECV) epithelial and Langerhans precursor (LP) cells. Tissue culture conditions were developed to induce these cells to differentiate into a three-dimensional, organotypic tissue. Characterization showed that the tissue reproduced many of the histological, ultrastructural, and protein expression properties of native tissue. Initial experiments demonstrated the utility of the tissue model for predicting ECV irritation and for HIV infection/ transmission studies. Finally, an economic assessment of the costs involved in producing such tissues showed that the ECV tissue product appears to be commercially feasible. The Phase II work plan will expand upon the results of Phase I to further develop the ECV tissue model. Culture conditions will be optimized and the tissue will be thoroughly characterized. Protocols for irritation studies will be finalized and the mechanisms of HIV infection and transmission in the tissue will be delineated. Finally, methodology for testing HIV microbicides will be developed.